The invention relates to the area of damping devices. Specifically, it relates to devices employing a resilient element operable in frictional contact with another member for generating damping forces.
Various devices are known which utilize resilient elastomer elements to produce a damping force to control or minimize shock and/or vibration or to generate a locking function. In such prior art devices, the resilient elastomer element is in frictional engagement with another member.
Such devices are, for example, disclosed in U.S. Pat. No. 5,720,369 to Thorn entitled xe2x80x9cAdjustable, Lockable Devices,xe2x80x9d U.S. Pat. No. 5,634,537 to Thorn entitled xe2x80x9cLocking and Positioning Device,xe2x80x9d U.S. Pat. No. 5,613,580 to Young entitled xe2x80x9cAdjustable, Lockable Strutxe2x80x9d, U.S. Pat. No. 5,257,680 to Corcoran et al. entitled xe2x80x9cSurface Effect Dampers Having Both A Hysteresis and A Frictional Component, U.S. Pat. No. 5,183,137 to Siwek et al. xe2x80x9cDual Rate Surface Effect Dampersxe2x80x9d U.S. Pat. No. 4,964,516 to Thorn entitled xe2x80x9cDamped Extended-Motion Strut,xe2x80x9d U.S. Pat. No. 4,957,279 to Thorn entitled xe2x80x9cFluidless Multi-Directional Motion-Damping Mount,xe2x80x9d U.S. application Ser. No. 09/040,694 to Thorn et al. entitled xe2x80x9cResistance Generating Device,xe2x80x9d and U.S. application Ser. No. 09/040,694 to Miller et al. entitled xe2x80x9cElastomer Damper,xe2x80x9d all of which are commonly assigned to the assignee of the present invention.
Although these devices are adequate for their intended purposes, they each exhibit certain inadequacies that make them unattractive candidates for providing damping forces between relatively moveable members in low-cost applications. Moreover, many of the devices available heretofore include large numbers of components and provide damping forces that may vary significantly with tolerance variations.
Therefore, there is a long felt, and unmet, need for a simple, durable, maintenance free, and cost-effective damper for providing damping forces between relatively moveable members, and in particular, a damper configuration which is insensitive to tolerance variations due to manufacturing processes used to produce it.
The present invention provides a friction damper of simple construction including a resilient friction element in frictional engagement with a surface of another member. Moreover, the invention provides a damper exhibits excellent tolerance insensitive damping. The damper includes a tubular outer member and an inner member assembly reciprocatable therein. The tubular outer member includes a recess having an inner surface of preferably substantially constant diameter, and a first attachment hole radially intersecting the recess. The inner member assembly includes a shaft having a cross-wise directed second attachment hole and a resilient friction member preferably fixedly mounted (e.g., by bonding or mechanical fastening means) to the shaft. The resilient friction member is disposed in the recess in precompressed frictional contact with the inner surface of the outer member.
The tubular outer member is preferably open at its first and second ends and the constant diameter is preferably provided along its entire axial length. The shaft preferably includes a first dimension portion with a smaller dimension portion extending from it. The first dimension portion is preferably integral with the smaller dimension portion. Alternatively, the second portion may be a separate member which engages the first.
Various means may be employed for fixedly mounting the resilient friction member to the shaft. Most preferably, the friction member is bonded to the shaft. Alternatively, the smaller dimension portion may include a deformable portion that is deformed during assembly to secure the resilient friction member onto the shaft. According to another embodiment, the smaller dimension portion may include a taper on an end thereof and the shaft may include first and second steps thereon. During assembly the resilient friction member is received over the taper and snaps onto place between the steps. In another embodiment, a tinnerman-type lock washer is received over the end of shaft to fixedly secure the resilient friction member thereon.
As previously mentioned, in several other embodiments, a smaller dimension portion includes a separate member that engages a hole in the first dimension portion (e.g., a rivet or fastener). For example, the separate member may include a thread formed on the smaller dimension portion that engages a like thread formed on the hole. Moreover, the separate member may include one or more projections that snap into the first portion to retain the friction member in place.
According to a preferred embodiment, the resilient friction member preferably comprises at least one protrusion (most preferably a plurality of ribs) formed on an outer surface thereof. The ribs may be axially or radially oriented. These ribs are precompressed against the surface and allow significant variations in the tolerances of the members yet still providing adequate damping forces. Preferably, the resilient friction member is lubricated to provide more consistent damping and to minimize break away forces. If adjustment to the damping level is desired, one or more o-rings may be received over the resilient friction member thereby increasing its surface area.
In accordance with another embodiment of the invention, a plurality of undulations may be formed on the shaft for fixedly securing the resilient friction member to it. The undulations may be corrugations or jagged ridges over which the resilient friction member is received.
The damper according to the invention finds excellent utility for damping the movement of spring biased seatbacks. Therefore, according to another aspect of the invention, a tiltable seat assembly is provided which comprises a first seat member, a second seat member movably mounted on the first seat member, a spring biasing the second seat member relative to the first seat member and a damper including a resilient friction member linearly reciprocatable in an outer member interconnecting between the first and second seat members.
In more detail, a preferred embodiment of the damper comprises a tubular outer member including first and second open ends, a recess having an inner surface of substantially constant diameter, and a first attachment hole intersecting the recess at the first end thereof; and an inner member assembly received in the second end having a shaft with a first portion including a second attachment hole formed therein and a smaller dimension portion extending therefrom, and a resilient friction member fixedly mounted to the smaller dimension portion, the resilient friction member disposed in the recess in frictional contact with the inner surface.
According to another aspect, the invention comprises a tiltable seat assembly having a first seat member, a second seat member movably mounted on the first seat member, a spring biasing the second seat member relative to the first seat member, and a damper interconnected between the first and second seat members, the damper further comprising a first member having an engagement surface and attaching to one of the first and the second seat members, and a second member linearly reciprocatable relative to the first member and attaching to the other of the first and second seat members, the second member including a resilient friction member disposed in frictional contact with the engagement surface wherein the damper provides damping between the first and second seat members.
It is an advantage of the invention is that it provides a damper with simple, durable and low-cost construction.
Another advantage of the invention is that it provides adequate damping forces over relatively broad tolerance ranges.
Yet another advantage of the invention is that it provides cost-effective damping for controlling motion in spring-biased chairback applications.
The above-mentioned and further features, advantages and characteristics of the present invention will become apparent from the accompanying descriptions of the preferred embodiments and attached drawings.